The present invention relates to compounds having pharmaceutical properties, and in particular, to compounds useful for preventing and treating central nervous system (CNS) disorders. The present invention relates to a method for treating patients suffering from or susceptible to such disorders, and in particular, to a method for treating patients suffering from those disorders which are associated with neurotransmitter system dysfunction. The present invention also relates to compositions of matter useful as pharmaceutical compositions in the prevention and treatment of CNS disorders which have been attributed to neurotransmitter system dysfunction.
CNS disorders are a type of neurological disorder. CNS disorders can be drug induced; can be attributed to genetic predisposition, infection or trauma; or can be of unknown etiology. CNS disorders comprise neuropsychiatric disorders, neurological diseases and mental illnesses; and include neurodegenerative diseases, behavioral disorders, cognitive disorders and cognitive affective disorders. There are several CNS disorders whose clinical manifestations have been attributed to CNS dysfunction (i.e., disorders resulting from inappropriate levels of neurotransmitter release, inappropriate properties of neurotransmitter receptors, and/or inappropriate interaction between neurotransmitters and neurotransmitter receptors). Several CNS disorders can be attributed to a cholinergic deficiency, a dopaminergic deficiency, an adrenergic deficiency and/or a serotonergic deficiency. CNS disorders of relatively common occurrence include presenile dementia (early onset Alzheimer's disease), senile dementia (dementia of the Alzheimer's type), Parkinsonism including Parkinson's disease, Huntington's chorea, tardive dyskinesia, hyperkinesia, mania, attention deficit disorder, anxiety, dyslexia, schizophrenia and Tourette's syndrome.
Senile dementia of the Alzheimer's type (SDAT) is a debilitating neurodegenerative disease, mainly afflicting the elderly; characterized by a progressive intellectual and personality decline, as well as a loss of memory, perception, reasoning, orientation and judgment. One feature of the disease is an observed decline in the function of cholinergic systems, and specifically, a severe depletion of cholinergic neurons (i.e., neurons that release acetylcholine, which is believed to be a neurotransmitter involved in learning and memory mechanisms). See, Jones, et al., Intern. J. Neurosci., Vol. 50, p. 147 (1990); Perry, Br. Med. Bull., Vol. 42, p. 63 (1986) and Sitaram, et al., Science, Vol. 201, p. 274 (1978). It has been observed that nicotinic acetylcholine receptors, which bind nicotine and other nicotinic agonists with high affinity, are depleted during the progression of SDAT. See. Giacobini, J. Neurosci. Res., Vol. 27, p. 548 (1990); and Baron, Neurology, Vol. 36, p. 1490 (1986). As such, it would seem desirable to provide therapeutic compounds which either directly activate nicotinic receptors in place of acetylcholine or act to minimize the loss of those nicotinic receptors.
Certain attempts have been made to treat SDAT. For example, nicotine has been suggested to possess an ability to activate nicotinic cholinergic receptors upon acute administration, and to elicit an increase in the number of such receptors upon chronic administration to animals. See, Rowell, Adv. Behav. Biol., Vol. 31, p. 191 (1987); and Marks, J. Pharmacol. Exp. Ther., Vol. 226, p. 817 (1983). It also has been proposed that nicotine can act directly to elicit the release of acetylcholine in brain tissue, to improve cognitive functions, and to enhance attention. See, Rowell, et al., J. Neurochem., Vol. 43, p. 1593 (1984); Sherwood, Human Psychopharm., Vol. 8, pp. 155-184 (1993); Hodges, et al., Bio. of Nic., Edit. by Lippiello, et al., p. 157 (1991 ); Sahakian, et al., Br. J. Psych., Vol. 154, p. 797 (1989); and U.S. Pat. Nos. 4,965,074 to Leeson and 5,242,935 to Lippiello et al. Other methods for treating SDAT have been proposed, including U.S. Pat. Nos. 5,212,188 to Caldwell et al. and 5,227,391 to Caldwell et al. and European Patent Application No. 588,917. Another proposed treatment for SDAT is Cognex, which is a capsule containing tacrine hydrochloride, available from Parke-Davis Division of Warner-Lambert Company, which reportedly preserves existing acetylcholine levels in patients treated therewith.
Parkinson's disease (PD) is a debilitating neurodegenerative disease, presently of unknown etiology, characterized by tremors and muscular rigidity. A feature of the disease appears to involve the degeneration of dopaminergic neurons (i.e., which secrete dopamine). One symptom of the disease has been observed to be a concomitant loss of nicotinic receptors which are associated with such dopaminergic neurons, and which are believed to modulate the process of dopamine secretion. See, Rinne, et al., Brain Res., Vol. 54, pp. 167-170 (1991) and Clark, et al., Br. J. Pharm., Vol. 85, pp. 827-835 (1985). It also has been proposed that nicotine can ameliorate the symptoms of PD. See, Smith et al., Rev. Neurosci., Vol. 3(1), pp. 25-43 (1982).
Certain attempts have been made to treat PD. One proposed treatment for PD is Sinemet CR, which is a sustained-release tablet containing a mixture of carbidopa and levodopa, available from The DuPont Merck Pharmaceutical Co. Another proposed treatment for PD is Eldepryl, which is a tablet containing selefiline hydrochloride, available from Somerset Pharmaceuticals, Inc. Another proposed treatment for PD is Parlodel, which is a tablet containing bromocriptine mesylate, available from Sandoz Pharmaceuticals Corporation. Another method for treating PD and a variety of other neurodegenerative diseases has been proposed in U.S. Pat. No. 5,210,076 to Berliner et al.
Tourette's syndrome (TS) is an autosomal dominant neuropsychiatric disorder characterized by a range of neurological and behavioral symptoms. Typical symptoms include (i) the onset of the disorder before the age of 21 years, (ii) multiple motor and phonic tics although not necessarily concurrently, (iii) variance in the clinical phenomenology of the tics, and (iv) occurrence of quasi daily tics throughout a period of time exceeding a year. Motor tics generally include eye blinking, head jerking, shoulder shrugging and facial grimacing; while phonic or vocal tics include throat clearing, sniffling, yelping, tongue clicking and uttering words out of context. The pathophysiology of TS presently is unknown, however it is believed that neurotransmission dysfunction is implicated with the disorder. See, Calderon-Gonzalez et al., Intern. Pediat., Vol. 8(2), pp. 176-188 (1993) and Oxford Textbook of Medicine, Eds. Weatherall et al., Chapter 21.218 (1987).
It has been proposed that nicotine pharmacology is beneficial in suppressing the symptoms associated with TS. See, Devor et al., The Lancet, Vol. 8670, p. 1046 (1989); Jarvik, British J. of Addiction, Vol. 86, pp. 571-575 (1991); McConville et al., Am. J. Psychiatry., Vol. 148 (6), pp. 793-794 (1991); Newhouse et al., Brit. J, Addic., Vol. 86, pp. 521-526 (1991); McConville et al., Biol. Psychiatry, Vol. 31, pp. 832-840 (1992); and Sanberg et al., Proceedings from Intl. Syrup. Nic., S39 (1994). It also has been proposed to treat TS using Haldol, which is haloperidol available from McNeil Pharmaceutical; Catapres, which is clonidine available from Boehringer Ingelheim Pharmaceuticals, Inc., Orap, which is pimozide available from Gate Pharmaceuticals; Prolixin, which is fluphenazine available from Apothecon Division of Bristol-Myers Squibb Co.; and Klonopin, which is clonazepam available from Hoffmann-LaRoche Inc.
Attention deficit disorder (ADD) is a disorder which affects mainly children, although ADD can affect adolescents and adults. See, Vinson, Arch. Fam. Med., Vol. 3(5), pp. 445-451 (1994); Hechtman, J. Psychiatry Neurosci., Vol. 19 (3), pp. 193-201 (1994); Faraone et al., Biol. Psychiatry., Vol. 35(6), pp. 398-402 (1994) and Malone et al., J. Child Neurol., Vol. 9(2), pp. 181-189 (1994). Subjects suffering from the disorder typically have difficulty concentrating, listening, learning and completing tasks; and are restless, fidgety, impulsive and easily distracted. Attention deficit disorder with hyperactivity (ADHD) includes the symptoms of ADD as well as a high level of activity (e.g., restlessness and movement). Attempts to treat ADD have involved administration of Dexedrine, which is a sustained release capsule containing dextroamphetamine sulfate, available from SmithKline Beecham Pharmaceuticals; Ritalin, which is a tablet containing methylphenidate hydrochloride, available from Ciba Pharmaceutical Company; and Cylert, which is a tablet containing premoline, available from Abbott Laboratories. In addition, it has been reported that administration of nicotine to an individual improves that individual's selective and sustained attention. See, Warburton et al., Cholinergic control of cognitive resources, Neuropsychobiology, Eds. Mendlewicz, et al., pp 43-46 (1993).
Schizophrenia is characterized by psychotic symptoms including delusions, catatonic behavior and prominent hallucinations, and ultimately results in a profound decline in the psychosocial affect of the subject suffering therefrom. Traditionally, schizophrenia has been treated with Klonopin, which is available as a tablet containing clonezepam, available from Hoffmann-LaRoche Inc.; Thorazine, which is available as a tablet containing chlorpromazine, available from SmithKline Beecham Pharmaceuticals; and Clozaril, which is a tablet containing clozapine, available from Sandoz Pharmaceuticals. Such neuroleptics are believed to be effective as a result of interaction thereof with the dopaminergic pathways of the CNS. In addition, a dopaminergic dysfunction possessed by individuals suffering from schizophrenia has been proposed. See, Lieberman et al., Schizophr. Bull., Vol. 19, pp. 371-429 (1993) and Glassman, Amer. J. Psychiatry., Vol. 150, pp. 546-553 (1993). Nicotine has been proposed as being effective in effecting neurotransmitter dysfunction associated with schizophrenia. See, Merriam et al., Psychiatr. Annals, Vol. 23, pp. 171-178 (1993) and Adler et al., Biol. Psychiatry, Vol. 32, pp. 607-616 (1992).
Nicotine has been proposed to have a number of pharmacological effects. Certain of those effects may be related to effects upon neurotransmitter release. See, for example, Sjak-shie et al., Brain Res., Vol. 624, pp. 295-298 (1993), where neuroprotective effects of nicotine are proposed. Release of acetylcholine and dopamine by neurons upon administration of nicotine has been reported by Rowell et al., J. Neurochem., Vol. 43, pp. 1593-1598 (1984); Rapier et al., J. Neurochem., Vol. 50, pp. 1123-1130 (1988); Sandor et al., Brain Res., Vol. 567, pp. 313-316 (1991) and Vizi, Br. J. Pharmacol., Vol. 47, pp. 765-777 (1973). Release of norepinephrine by neurons upon administration of nicotine has been reported by Hall et al., Biochem. Pharmacol., Vol. 21, pp. 1829-1838 (1972). Release of serotonin by neurons upon administration of nicotine has been reported by Hery et al., Arch. Int, Pharmacodyn. Ther., Vol. 296, pp. 91-97 (1977). Release of glutamate by neurons upon administration of nicotine has been reported by Toth et al., Neurochem Res., Vol. 17,pp. 265-271 (1992). Therefore, it would be desirable to provide a pharmaceutical composition containing an active ingredient having nicotinic pharmacology, which pharmaceutical composition is capable of illicting neurotransmitter release within a subject in order to prevent or treat a neurological disorder. In addition, nicotine reportedly potentiates the pharmacological behavior of certain pharmaceutical compositions used for the treatment of certain CNS disorders. See, Sanberg et al., Pharmacol. Biochem. & Behavior, Vol. 46, pp. 303-307 (1993); Harsing et al.,J. Neurochem., Vol. 59, pp. 48-54 (1993) and Hughes, Proceedings from Intl. Symp. Nic., S40 (1994). Furthermore, various other beneficial pharmacological effects of nicotine have been proposed. See, Decina et al., Biol. Psychiatry, Vol. 28, pp. 502-508 (1990); Wagner et al., Pharmacopsychiatry, Vol. 21, pp. 301-303 (1988); Pomerleau et al., Addictive Behaviors, Vol. 9, p. 265 (1984); Onaivi et al., Life Sci., Vol. 54(3), pp. 193-202 (1994) and Hamon, Trends in Pharmacol, Res., Vol. 15, pp. 36-39.
It would be desirable to provide a useful method for the prevention and treatment of a CNS disorder by administering a nicotinic compound to a patient susceptible to or suffering from such a disorder. It would be highly beneficial to provide individuals suffering from certain CNS disorders with interruption of the symptoms of those diseases by the administration of a pharmaceutical composition which has nicotinic pharmacology and which has a beneficial effect upon the functioning of the CNS, but which does not provide any significant associated side effects (e.g., increased heart rate and blood pressure) attendant with interaction of that compound with cardiovascular sites. It would be highly desirable to provide a pharmaceutical composition incorporating a compound which interacts with nicotinic receptors which have the potential to affect the functioning of the CNS, but which does not significantly affect those receptors which have the potential to induce undesirable side effects (e.g., appreciable pressor cardiovascular effects and appreciable activity at skeletal muscle sites).